37 Notornis, 2016, Vol. 63: 37-39 0029-4470 © The Ornithological Society of New Zealand Inc. SHORT NOTE Artificial light at night potentially alters feeding behaviour of the native southern black-backed gull (Larus dominicanus) ANDREW R. PUGH* Scion, Forest Protection, 49 Sala Street, Rotorua, New Zealand STEPHEN M. PAWSON Scion, Forest Protection, Forestry Rd, Ilam, Christchurch, New Zealand Artificial light at night (ALAN) is increasingly & Bader 2014). The blue light part of the spectra is recognised as having ecological impacts. In fact, highly visible across a wide range of animal groups artificial light has been identified as one of the (Davies et al. 2013). most serious emerging threats to urban ecosystems Artificial light is known to cause behavioural (Stanley et al. 2015). Rich (2005) documents some changes in birds. There are periodic reports of mass of the first observations of the impact of artificial death of migrating birds from impact or exhaustion lights, beginning over 150 years ago. Since then, as a result of specific point source lights, the most light pollution has continued to grow in scale and famous example being the death of approximately in the number of known impacts on wildlife. It was 50,000 birds due to exhaustion over 2 nights at estimated that 18.7% of the world’s global land area an air force base in the United States (Johnston is now affected to some extent by ALAN (Cinzano 1955). However, additional, more subtle, effects et al. 2001), and is increasing by approximately 6% on birds include inducing activity earlier in the annually (Hölker et al. 2010), due in part to new day (Kempenaers et al. 2010; Dominoni et al. 2014), energy efficient lighting technologies, such as light and altering the timing of breeding (Kempenaers emitting diodes (LEDs). These new technologies et al. 2010). Attention is now being drawn to the may exacerbate some of these problems further multitude of problems arising across ecosystems because of the larger proportion of blue light (e.g., Davies et al. 2014; Gaston et al. 2014) caused by emitted compared to older lighting technology ALAN. To date there are few studies that record the (Davies et al. 2013; Gaston et al. 2014). LEDs have impact of ALAN on avian feeding behaviour. a peak of blue-green light not present in other The southern black-backed gull (Larus lighting technologies such as high pressure sodium dominicanus) inhabits both marine and terrestrial or metal halide lighting (Davies et al. 2013; Pawson environments in New Zealand (Powlesland & Powlesland 1994; Maloney 1999). It has adapted to Received 6 December 2015; accepted 25 February 2016 the significant anthropogenic changes throughout *Correspondence: [email protected] the landscape, and now inhabits a number of 38 Short note modified areas, including farms and rubbish dumps in New Zealand to adopt LED technology. For (Powlesland & Powlesland 1994). The southern example, it is reported in the media that Auckland black-backed gull has been recorded foraging at City plans to change 44% of its 100,000 street lights night under lights in a marine environment before, from high pressure sodium lighting to LED lighting but “… only one or two…” (Leopold et al. 2010). (Anonymous 2014a). Wellington city is also in the However, during night time visits to multiple wood process of adopting LED technology (Anonymous processing sites that have ALAN, the authors and 2014b). While we acknowledge the importance of sawmill workers have observed significant changes seeking more energy efficient lighting solutions, in the natural behaviour of this native bird that this change may increase the ecological impacts of suggest they are using ALAN to increase the time ALAN by changing the spectral composition of street spent foraging. lighting. Given the scope of such change in municipal The authors have observed southern black- lighting, it is important that consideration is given to backed gulls congregating on the roofs of the potential ecological impacts from this substantial buildings when adult burnt pine longhorn beetle change to artificial night lighting. To minimise the (Cerambycidae: Arhopalus ferus) and huhu beetle impacts of ALAN, 3 methods have been proposed: (Cerambycidae: Prionoplus reticularis) are flying use of light shields to direct light downwards, at night during summer. These observations are reduction in number of lights used, and use of light corroborated by sawmill owners in Nelson and the sources that avoid emitting light from the blue part Hawke’s Bay who confirm that there are regular of spectrum (Navara & Nelson 2007). It is imperative annual congregations that coincide with peak insect that the impacts of increasing the area affected by emergence periods. These beetle species, like many ALAN and a change in the spectral composition is Cerambycidae, are highly attracted to artificial light, carefully considered and examined before wide- particularly the white lighting (which has a blue scale adoption of new lighting technologies occurs. wavelength peak) used to illuminate log yards at saw mills (Pawson & Watt 2009; Pawsonet al. 2009). Approximately 1 hour prior to sunset the gulls can ACKNOWLEDGMENTS Emily Fountain, Victoria Smith, and Manu Somerville be seen circling above sawmills and adjacent forest whose valuable discussions and encouragement led to stands. Prior to sunset, as beetles take flight, the the creation of this manuscript. Cecilia Romo and Thomas gulls can be seen chasing the flying insects. The Paul for their helpful comments on an earlier version of most common insect at sawmills is the smaller burnt this manuscript. Thanks to the anonymous reviewers who pine longhorn beetle and they can be clearly seen improved the clarity and content of this article. with gulls in pursuit. As night falls the gulls begin to fly in concentrated clusters (estimated number 5-20) around the lights, probably taking various LITERATURE CITED Anonymous. 2014A. Upgrade to white light for Auckland insects on the wing. This behaviour was observed roads. 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